Topical microbicides are products designed to prevent the sexual transmission of HIV and other disease pathogens. Studies have shown that nonoxynol-9, a detergent microbicide, can cause mucosal erosion and ulceration and increased risk of HIV infection. Attention has been given to developing non-detergent topical microbicides, such as BufferGel and PRO 2000/5 Gel. Studies have shown these products to be safe and acceptable for vaginal use [AS PER AMENDMENT 08/20/01: "however, none of the clinical studies to date have investigated the effects on the penile epithelium and urethral mucosa" has been replaced with: Phase I trials also have been conducted to assess the safety of BufferGel and PRO 2000/5 Gel (P) on the penile epithelium and urethral mucosa. In 1 trial, HIV-uninfected men applied either PRO 2000/5 or a gel containing the inactive ingredients of PRO 2000/5 for 7 days. A few patients reported mild symptoms of genital itching, tingling, irritation, dryness, discoloration, or flaking of the dried gel. In a similar trial comparing BufferGel and K-Y Jelly, a few patients reported similar symptoms.] It is important to determine whether the frequency and severity of adverse events experienced by men is comparable to that observed among women. It is also important to determine whether these adverse events are similar between circumcised and uncircumcised men.